Edwabd thompsosy of hokah



(No Model.)

' E. THOMPSON. v PROCESS OF MAKING PULP PROM WOOD AND OTHER FIBROUS MATERIAL Patented Nov 6, 1883 a. vzrzns mum i m mammac,

- w 0od by means of grinding -stones.

UNITED STATES:

PATENT OFFICE,

EDWARD THOMPSON, OF HOKAH, MINNESOTA:

,PROCESS OF MAKING PULP FROM WOOD AND OTHER FIBROUS MATERIAL.

SPECIFICATION forming part of Letters Patent No. 287,980, dated November 6, 1883. Application filed September 21, 1883. (No modem -.'Zo all whom, it may concern.-

Be it known that I, EDWARD THOMPSON, a citizen of theIlnited States, residing at Hokah, in the county of Houston and State of Minnesota, have invented certain new and useful Improvements in Process'of Making Pulp from "Wood and other Fibrous Material; and I do hereby declare the following to be a full, clear,

the operation as heretofore practiced, in order to clearly distinguish previous modes of treatment and their results from the within-v described improvementand its results, which will be hereinafter fully set forth. 2o

Hitherto in reducing wood .to pulp the process consisted in tearing or cutting the Sometimes logs or bolts were applied to the grinding-surface, and sometimes the wood was previously cut into small blocks or pieces by saws, knives, and their equivalents. In direct grinding from the log the wood has been ap- "lel with the grinding-surface. 3

' the grinding process, 4

remaining blocks of the series, and was disries, when finally discharged, exhibited as many grades as there'were blocks; and it was plied with the endgrain oblique to or paral- In' the first and second namedways the wood was ground to dust, the fibers being cut so short as to be destroyed. and rendered practically of little value. In the third-named case the fibers were torn font in more or less unequal masses, greatly varying in length. To obviate this disadvantage the fibers were subjected to regrinding by being required to pass through grindingstones, and other blocks likewise undergoing By this process the fiber which was torn from the first block in the series was successively passed under the charged in company with fibers derived from each of the succeeding blocks. These fibers, having undergone less regrinding, according to the remove from the terminus of the setherefore necessary to separate and assort or grade the fibers for different uses, according to their grade. In all these modes it was I necessary to press the block against the grinding-stone with great force, and even though water may have been employed to facilitate the abrasion the great pressure of the block upon the stone excluded the water and made the process one of dry grinding, with a large percentage'of useless waste in the form of dust.

I am aware that wood has heretofore been reduced to pulp by passing it through a series of grinding-stones; but, so far as I know, the

fiber has been fed into the first grinding-stone in its normal condition as to dryness; and 21- though water is simultaneously fed into the grinding; stone the pieces do not have time toabsorb moisture sufficient to prevent the central parts from being abraded in a dry state, thus materially shortening the length of the fiber.

The object of my improvement, as herein described, is the gradual reduction of wood, sawdust, or other fibrous material to pulp, and at the same time preserve, as far as possible, the length of the fibers thereof, by a pcculiar use of water in the earlier stages of the operation to soften the tissues connecting the fibers, and make the water serve as a lubricant to prevent them from abrading each other, and thereby making the material tougher and more pliable. I thus enable it to better withstand the tendency to break 'and shorten the fibers.

My process is applicable to the reduction of fibers other than wood or wood sawdust; but for convenience I will describe its operation in the reduction of sawdustor wood to pulp without intending to confine its application thereto.

' v The initial and distinctive feature of my improvement consists in first feeding the material in a moistened condition between and through revolving rollers having a slight differential motion, and there subjecting it to a pressure sufficient to severthe adhesive tissues connecting the fiber, thereby rendering its reduction to pulp more rapid and easy. After passing it through the rollers it is deposited in a soaking-vat, and there allowed to remain until it is thoroughly saturated and sufiicient- 1y mixed with water to cause it to run freely. In thiscondition it is fed into a series of grinding-stones of the ordinary burr or millstone variety, for the purpose of gradually reducing it to therequired fineness, the stones having a special dress suitable to the purpose of preserving the fibers during the process of reduction. As the process of reduction is carried on, more water is added, as is necessary to make it run through the stones freely. Each of the series of stones is thus enabled to separatethe fiber with the least possible injury thereto, making a much better quality of pulp than heretofore and at less cost. This process may be carried on by using two, three, or four sets of grinding-stones, according to the obstinacy of the material used, in order that the reduction may be gradual and not violent. The advantage of using rollers on the first reduction is very great, the nature of wood being such that. any violent abrasion of large pieces breaks the fiber, thus deteriorating the quality of the pulp; but by giving it such pressure between the rollers as to simply break down the cellular tissue, and thus overcome the adhesion of the fibers, we can preserve their greater length. This has been done in some instances by concussion and hammering with good results; but on account of it being a slow process it has not come into general use.

In the preparation of the'stones for the practice of the within-described improved process I discard the usual dress of cracking the lands between the furrows, but, instead, use a dress composed of a series of ordinary furrows, as used in wheat-grinding, with the new feature of dress, dividing the lands between the furrows into a number of fine and very smooth furrows having the shape of a united semiserration and semi-corrugation. through which the fiber is first passed has less furrows and larger dressing than the dress of the stones through which the fiber is afterward fed, as the dress is increased in fineness to make it correspond with each successive reduction of the fiber. The motion of the stone is to be in such direction that the semi-serration will lead the semi-corrugation, and thus separate the fiber by a rubbing instead of a cutting process.

I hereby expressly reserve the right to make the special dress of grinding-stones herein de-.

scribed the subject of separate Letters Patent.

I do not, as some others, run the principal furrows out near the periphery of the stone, which plan destroys the draft, thereby keeping the material too long under the stone after it has been sufficiently reduced, tothe greatdamage of the finer fibers, my object beingto pass it through quicklyfrom one set to the required fineness with the least possible injury to the fiber.

A drawing substantially representing the mechanism herein described isherewith filed as part hereof for the purpose, of illustrating the mode of practicing the process set forth.

' desired.

. frames attached to roller-frame a.

The stone Said drawing is a side elevation of the machinery, partly in section.

A refers to the revolving rollers, having differential motion by reason of gearing arranged for that purpose. These rollers are drivenby belt Q through pulley P by power located as O is a hopper through which the reduced wood or other material is automatically fed, revolving feeder g, driven by belt 19, operating pulley p. The hopper O is supported by Below the rollers is a chamber, a", through whichthe fiber passes into the soaking-vat B, which is supplied with water by a pipe, N, having valve n. The soaked fiber is carried through pipe 0 and its connection 0 into grinding stone hopper D.

Overthe hoppers D is a water-pipe, J, having valves Z,in proper position to conductedditional water into the stones, as previously set forth. The fiber, after workingthrough the grinding-stones E, passeszthroughv conduit F, having suitable connection with thegrindstone-point of issue, from thenceinto the receiving-chamber of the elevator H,with which the conduit 13 is connected. The elevator H is provided with pulleys working on shafting h" and h. The said pulleys carry endless belts provided with piston-blocks B, for raising the fiber through the elevator-Ways hand vator it passes into conduit K, and thence through its angular extension k into the hopper D of the stones E; thence onthrough the conduit F into and through elevator H and its angled conduit K k, into hopper D. of

stones E; thence on through the conduit E into elevator H, and through its angled conduit K 7.: into the final set of stones E, fromwhence it issues at outlet G in a finely-reduced state. The elevator issue conduits K worked by bevel-geared shafting M, connecting with beveled gear-ing on the elevator-shafting 71/.

a is thelfloorof thebuilding above the grind ing-stones. and the elevators with which. they are connected. of stones to the other, graduallymeducing it Having thus described my improved ii pro cess and explained the construction and; operation of the machinery for the; practice As the fiber rises to the top of theele- 2i moistened eonclition through revolving roll- In testimony whereof Ihave affixed my sigers, and then depositing it in a soakingat, nature, in presence of twewitnesses, this 21st 10 and there thoroughly saturating and mixing day of September, 1883.

it with water snffieiently to make it run freely Y M T 5 and afterward feeding it in this conditioii EDW ARD THOMPSOI throughe series of grinding-stones for the pur- @Vitnesses:

pose of reducing it to the required fineness, JOHN C. MILLER,

substantially as set; forth. I V XV. S. 0. SMITH. 

